[PATCH iwl-next v3 7/9] ice: use u64_stats API to access pkts/bytes in dim sample

[Jacob Keller <jacob.e.keller@intel.com>]

The __ice_update_sample and __ice_get_ethtool_stats functions directly
accesses the pkts and bytes counters from the ring stats. A following
change is going to update the fields to be u64_stats_t type, and will need
to be accessed appropriately. This will ensure that the accesses do not
cause load/store tearing.

Add helper functions similar to the ones used for updating the stats
values, and use them. This ensures use of the syncp pointer on 32-bit
architectures. Once the fields are updated to u64_stats_t, it will then
properly avoid tears on all architectures.

Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
---
 drivers/net/ethernet/intel/ice/ice_lib.h     |  6 +++++
 drivers/net/ethernet/intel/ice/ice_ethtool.c | 26 +++++++++++++-------
 drivers/net/ethernet/intel/ice/ice_lib.c     | 36 ++++++++++++++++++++++++++++
 drivers/net/ethernet/intel/ice/ice_txrx.c    | 29 +++++++++++-----------
 4 files changed, 75 insertions(+), 22 deletions(-)

diff --git a/drivers/net/ethernet/intel/ice/ice_lib.h b/drivers/net/ethernet/intel/ice/ice_lib.h
index 2cb1eb98b9da..49454d98dcfe 100644
--- a/drivers/net/ethernet/intel/ice/ice_lib.h
+++ b/drivers/net/ethernet/intel/ice/ice_lib.h
@@ -92,6 +92,12 @@ void ice_update_tx_ring_stats(struct ice_tx_ring *ring, u64 pkts, u64 bytes);
 
 void ice_update_rx_ring_stats(struct ice_rx_ring *ring, u64 pkts, u64 bytes);
 
+void ice_fetch_tx_ring_stats(const struct ice_tx_ring *ring,
+			     u64 *pkts, u64 *bytes);
+
+void ice_fetch_rx_ring_stats(const struct ice_rx_ring *ring,
+			     u64 *pkts, u64 *bytes);
+
 void ice_write_intrl(struct ice_q_vector *q_vector, u8 intrl);
 void ice_write_itr(struct ice_ring_container *rc, u16 itr);
 void ice_set_q_vector_intrl(struct ice_q_vector *q_vector);
diff --git a/drivers/net/ethernet/intel/ice/ice_ethtool.c b/drivers/net/ethernet/intel/ice/ice_ethtool.c
index 0bc6f31a2b06..6c93e0e91ef5 100644
--- a/drivers/net/ethernet/intel/ice/ice_ethtool.c
+++ b/drivers/net/ethernet/intel/ice/ice_ethtool.c
@@ -1942,25 +1942,35 @@ __ice_get_ethtool_stats(struct net_device *netdev,
 	rcu_read_lock();
 
 	ice_for_each_alloc_txq(vsi, j) {
+		u64 pkts, bytes;
+
 		tx_ring = READ_ONCE(vsi->tx_rings[j]);
-		if (tx_ring && tx_ring->ring_stats) {
-			data[i++] = tx_ring->ring_stats->stats.pkts;
-			data[i++] = tx_ring->ring_stats->stats.bytes;
-		} else {
+		if (!tx_ring || !tx_ring->ring_stats) {
 			data[i++] = 0;
 			data[i++] = 0;
+			continue;
 		}
+
+		ice_fetch_tx_ring_stats(tx_ring, &pkts, &bytes);
+
+		data[i++] = pkts;
+		data[i++] = bytes;
 	}
 
 	ice_for_each_alloc_rxq(vsi, j) {
+		u64 pkts, bytes;
+
 		rx_ring = READ_ONCE(vsi->rx_rings[j]);
-		if (rx_ring && rx_ring->ring_stats) {
-			data[i++] = rx_ring->ring_stats->stats.pkts;
-			data[i++] = rx_ring->ring_stats->stats.bytes;
-		} else {
+		if (!rx_ring || !rx_ring->ring_stats) {
 			data[i++] = 0;
 			data[i++] = 0;
+			continue;
 		}
+
+		ice_fetch_rx_ring_stats(rx_ring, &pkts, &bytes);
+
+		data[i++] = pkts;
+		data[i++] = bytes;
 	}
 
 	rcu_read_unlock();
diff --git a/drivers/net/ethernet/intel/ice/ice_lib.c b/drivers/net/ethernet/intel/ice/ice_lib.c
index 26d17813f426..897df9362638 100644
--- a/drivers/net/ethernet/intel/ice/ice_lib.c
+++ b/drivers/net/ethernet/intel/ice/ice_lib.c
@@ -3474,6 +3474,42 @@ void ice_update_rx_ring_stats(struct ice_rx_ring *rx_ring, u64 pkts, u64 bytes)
 	u64_stats_update_end(&rx_ring->ring_stats->syncp);
 }
 
+/**
+ * ice_fetch_tx_ring_stats - Fetch Tx ring packet and byte counters
+ * @ring: ring to update
+ * @pkts: number of processed packets
+ * @bytes: number of processed bytes
+ */
+void ice_fetch_tx_ring_stats(const struct ice_tx_ring *ring,
+			     u64 *pkts, u64 *bytes)
+{
+	unsigned int start;
+
+	do  {
+		start = u64_stats_fetch_begin(&ring->ring_stats->syncp);
+		*pkts = ring->ring_stats->pkts;
+		*bytes = ring->ring_stats->bytes;
+	} while (u64_stats_fetch_retry(&ring->ring_stats->syncp, start));
+}
+
+/**
+ * ice_fetch_rx_ring_stats - Fetch Rx ring packet and byte counters
+ * @ring: ring to read
+ * @pkts: number of processed packets
+ * @bytes: number of processed bytes
+ */
+void ice_fetch_rx_ring_stats(const struct ice_rx_ring *ring,
+			     u64 *pkts, u64 *bytes)
+{
+	unsigned int start;
+
+	do  {
+		start = u64_stats_fetch_begin(&ring->ring_stats->syncp);
+		*pkts = ring->ring_stats->pkts;
+		*bytes = ring->ring_stats->bytes;
+	} while (u64_stats_fetch_retry(&ring->ring_stats->syncp, start));
+}
+
 /**
  * ice_is_dflt_vsi_in_use - check if the default forwarding VSI is being used
  * @pi: port info of the switch with default VSI
diff --git a/drivers/net/ethernet/intel/ice/ice_txrx.c b/drivers/net/ethernet/intel/ice/ice_txrx.c
index 30073ed9ca99..f0f5133c389f 100644
--- a/drivers/net/ethernet/intel/ice/ice_txrx.c
+++ b/drivers/net/ethernet/intel/ice/ice_txrx.c
@@ -1087,35 +1087,36 @@ static void __ice_update_sample(struct ice_q_vector *q_vector,
 				struct dim_sample *sample,
 				bool is_tx)
 {
-	u64 packets = 0, bytes = 0;
+	u64 total_packets = 0, total_bytes = 0, pkts, bytes;
 
 	if (is_tx) {
 		struct ice_tx_ring *tx_ring;
 
 		ice_for_each_tx_ring(tx_ring, *rc) {
-			struct ice_ring_stats *ring_stats;
-
-			ring_stats = tx_ring->ring_stats;
-			if (!ring_stats)
+			if (!tx_ring->ring_stats)
 				continue;
-			packets += ring_stats->stats.pkts;
-			bytes += ring_stats->stats.bytes;
+
+			ice_fetch_tx_ring_stats(tx_ring, &pkts, &bytes);
+
+			total_packets += pkts;
+			total_bytes += bytes;
 		}
 	} else {
 		struct ice_rx_ring *rx_ring;
 
 		ice_for_each_rx_ring(rx_ring, *rc) {
-			struct ice_ring_stats *ring_stats;
-
-			ring_stats = rx_ring->ring_stats;
-			if (!ring_stats)
+			if (!rx_ring->ring_stats)
 				continue;
-			packets += ring_stats->stats.pkts;
-			bytes += ring_stats->stats.bytes;
+
+			ice_fetch_rx_ring_stats(rx_ring, &pkts, &bytes);
+
+			total_packets += pkts;
+			total_bytes += bytes;
 		}
 	}
 
-	dim_update_sample(q_vector->total_events, packets, bytes, sample);
+	dim_update_sample(q_vector->total_events,
+			  total_packets, total_bytes, sample);
 	sample->comp_ctr = 0;
 
 	/* if dim settings get stale, like when not updated for 1

-- 
2.51.0.rc1.197.g6d975e95c9d7